Highly sensitive and real-time detection of sialic acid using a solution-gated graphene transistor functionalized with carbon quantum dots

Sialic acid (SA) involves multiple different physiological and pathological processes. The SA level in serum is a reliable biomarker for the early diagnosis of malignant tumors. In this study, a new type of solution-gated graphene transistor was designed and fabricated for highly sensitive and real-time detection of SA by rapid binding of boric acid groups to diol monosaccharides. The gate electrode was modified with synthesized carbon quantum dots having boronic acid on the surface as the specific recognition site of SA. The detection of SA is achieved via the change of the gate surface potential after the conjugation of SA with carbon quantum dots. The device sensitivity can reach 10-19 M and a good linear relationship was present between the electrical current response and logarithmic values of the SA concentrations in the range of 10-19 M to 10-5 M. This sensor also exhibited good selectivity and good stability. Furthermore, the detection of SA in simulated serum samples was also carried out and satisfactory results were acquired, showing the high potential of the prepared sensor in clinical application.